1. Field of the Invention
The present invention relates to a water jacket (water jacket) structure of a cylinder head (cylinder head). A lower exhaust collecting portion and an upper exhaust collecting portion configured in a manner of being overlapped in an up-and-down direction, a lower water jacket configured below the lower exhaust collecting portion, and an upper water jacket configured above the upper exhaust collecting portion are formed inside a cylinder head. Cooling water is independent of one another and flows in a same direction inside the lower water jacket and the upper water jacket.
2. Description of Related Art
In a water-cooled in-line four-cylinder engine, according to the following Patent Document 1, the following water jacket structure of a cylinder head is already well-known. By means of the water jacket structure of a cylinder head, a lower exhaust collecting portion formed by integration of exhaust ports of a #1 cylinder and a #4 cylinder and an upper exhaust collecting portion formed by integration of exhaust ports of a #2 cylinder and a #3 cylinder are configured in a manner of being overlapped in an up-and-down direction, and a lower water jacket and an upper water jacket are formed in a manner of sandwiching the exhaust ports in the up-and-down direction, so that a middle water jacket communicated with the lower water jacket and the upper water jacket is configured between the lower exhaust collecting portion and the upper exhaust collecting portion. Therefore, by using cooling water flowing through the middle water jacket, cooling effects of vicinity, of the lower exhaust collecting portion and the upper exhaust collecting portion, that easily reaches a high temperature are improved.